Proponents of desktop virtualization have many reasons to advocate the technology over traditional PCs, including opportunities for reducing energy costs, centralizing desktop administration, increasing security and providing flexible work environments for end users.

But there are two sides to every story. Shifting to PC virtualization can raise new management challenges, require significant data center architecture changes, and introduce costs that can make a return on investment elusive.

Adoption of desktop virtualization remains scarce, although interest is high among enterprises, as many mull an overdue desktop refresh. A lousy economy coupled with disinterest in Windows Vista led many companies to delay upgrading their desktops. Now that Windows 7 is available and the economy is stabilizing, there's renewed interest in retooling the desktop infrastructure including desktop virtualization.

An ITIC survey of more than 800 businesses worldwide shows that 31% of respondents plan to implement a virtual desktop infrastructure in 2010, more than double the amount from the previous year. A related technology, application virtualization, is also on the rise, with 37% of respondents planning implementations -- an increase from 15% the previous year. Likewise, Gartner has found that 33% of organizations plan to deploy hosted virtual desktops in 2010.

With virtual desktops, users can access their applications and data from any machine. Administration can be easier for IT teams, since operating systems and data are centralized. PC backups can be easier to conduct, and some companies find virtual desktops improve business continuity and disaster recovery operations.

For instance, there's the classic hosted blade PC, a one-for-one swap where a single machine in the data center supports a single desktop. Or, companies can consider hosted shared desktops, where all processing happens on the server side and a server can support as many as 500 desktops. Similarly, hosted virtual machine-based desktops depend on a server-based virtual machine supporting dozens of desktops. Another option is a streamed desktop, where the operating system and apps execute locally, but the operating system and the apps are maintained centrally and streamed down when the device boots.

As companies consider which flavor of desktop virtualization is best for their environments, IT teams need to weigh the associated network and storage requirements.

"Because [hosted virtual desktops] replace PC internal hard disks with shared and centralized storage, organizations planning deployments need to prepare for increased storage capacity, not only for end users' immediate and future needs, but also for enterprise purposes — data management, backup and provisioning," wrote Mark Margevicius, a vice president and research director at Gartner, in a 2010 report.

Moving operating systems and applications inside the data center can create network issues and performance problems. Companies may need to increase bandwidth or deploy WAN optimization devices to combat latency and speed delivery of applications to end users.

Inside the data center, power, cooling and space issues must be ironed out. "IT managers may want to build new data centers or build out existing ones to accommodate additional storage and servers. They may also want to configure existing servers and storage systems for maximum capacity, which may involve data center renovation," writes Margevicius.

Analysts estimate choosing virtual desktops can cost 150% to 250% more than traditional PCs — and that's just for the direct cost of acquiring the technology. When you add in indirect costs, the ROI becomes difficult to quantify.

"Desktop virtualization is a lot like hybrid cars. No one disputes the value and they love the idea, but it is just too expensive to write a check and pay a lot when the traditional version is cheaper and already paid for," Gartner's Margevicius said in an interview with Network World.

Burton Group analyst Chris Wolf believes 2010 will be the year enterprises "kick the tires," and start small pilots. But even those who adopt desktop virtualization aren't likely to virtualize their entire desktop infrastructures right away. "In terms of wholesale virtualization of the desktop, I don't think we're anywhere close at this point."